The present invention relates to a reflow soldering method and system therefor in which electronic parts are soldered on a circuit substrate by heat gas obtained by heating air or the like, and particularly to a reflow soldering method and system therefor which facilitates temperature adjustment of a temperature equalizing portion in a preheating chamber and individually changes temperatures of the heat gas according to heat capacity widthwise of the circuit substrate.
In the past, a dipping method and a jet method have been used to solder electronic parts on a circuit substrate. Recently, with a trend toward high density and a trend toward surface packaging of packaging substrates, a reflow method has been widely used as a soldering method in view of reliability and productivity.
A typical reflow soldering is a vapor reflow method in which an object to be treated is put into a saturated vapor generated by heating and boiling a fluorine system inert liquid as a heat medium, and the object is evenly heated by latent heat to carry out soldering. This technology is disclosed, for example, in Japanese Patent Laid-Open No. 62-252670. The vapor reflow method is excellent in reliability and productivity but the heat medium is expensive and becomes consumed. Therefore, operating cost is high.
A reflow soldering apparatus using hot air, is disclosed, for example, in Japanese Patent Laid-Open No. 63-177960. This technique will be described hereinbelow with reference to FIGS. 21 and 22.
As shown in FIGS. 21 and 22, the reflow soldering apparatus comprises a preheating chamber first zone 1A, a preheating chamber second zone 2A, a reflow chamber 3A and a cooling chamber 4A. Hot air circulating mechanisms each comprising a heating heater 7 or an infrared face heater 16, a propeller fan 37 and a straightening plate 38 in the respective chambers are basically the same.
Hot air heated by the heating heater 7 or the infrared face heater 16 enters a side plate passage 39 from an outlet port 31 and moves upward, after which it is drawn into the propeller fan 37. The hot air elevated in pressure by the propeller fan 37 is straightened by the straightening plate 38 and is evenly blown against an object 11 to be treated from the top. The objects 11 are sequentially carried to the preheating chamber first zone 1A, the preheating chamber second zone 2A and the reflow chamber 3A by a conveyor 12 so that the objects 11 are heated under the adequate temperature condition and cooled by a cooling fan 13 in a cooling chamber 4A to complete soldering.
In FIGS. 21 and 22, reference numerals 14, 15 and 20 designate a driving sprocket wheel, an idler and a driving motor, respectively, for driving the conveyor 12.